1. Field of the Invention
This invention relates to an oven muffle having a receiving space, at least some regions of which are delimited by wall elements, in which at least one of the wall elements is permeable to IR radiation or has a region that is permeable to IR radiation.
2. Discussion of Related Art
Electrically heated ovens for freestanding ranges or for installation in a kitchen unit are known and essentially include an enameled oven muffle, which is heated from above and below with tubular heating elements. On the front side, the oven muffle is closed by a framed glass door. Usually, the upper heating system is positioned on the interior of the oven muffle and in high-end ovens, is also assisted by a second heating element that enables the oven to execute a grilling function. The lower heating element is attached to the outside of the muffle floor. In addition to these standard heating schemes for upper/lower heating and grilling mode, a recirculating air fan is frequently also incorporated into the back wall, which can also have a separate heating ring not only to recirculate air, but also to produce hot air itself. Because of the structural design and the materials used for the heating elements and oven muffle, the heating system as a whole is very sluggish. It takes a very long time for the tubular heating element to come to temperature and to assure a uniform temperature distribution in the oven. In particular, this applies to the lower heating element, which must first heat the muffle floor so that the muffle floor can then transmit the heat to the muffle chamber and to the food being cooked. Because the enameled walls absorb a great deal of the thermal energy produced by the tubular heating element, the whole muffle chamber including the walls is heated until a stationary temperature is reached. In addition to the long preheating time, there is also an additional problem that soiled regions, spattered grease, and the like become very stubbornly baked onto the walls of the oven muffle. Short wave IR radiation has been used to circumvent this shortcoming. A method for using this rapid thermal radiation for baking and frying procedures is described, for example, in PCT International Publication WO 00/40912 A2 and European Patent Reference EP 0 416 030 B1. The use of short wave IR radiation significantly increases the penetration depth into the food being cooked and speeds up the slow transmission of heat into the interior of the food by thermal conduction. A disadvantage of this technology is the use of point and linear heat sources, images of which appear directly on the food if no other optical preventive measures are taken.
A series of inventions attempt to eliminate these disadvantages, for example as taught in German Patent Reference DE 102 03 607 A1. In this case, an additional textured reflective layer mounted outside the translucent cover reflects the linear light source into the baking compartment. In addition, the linear light source also moves transversely in relation to its longitudinal span. The required movement apparatus makes this method very complex. The above-described oven also has a disadvantage that the reflecting wall is embodied in the form of an additional wall situated behind the translucent wall in the cooling conduit. As a result of this design, a part of the energy is carried away by the cooling conduit.
German Patent Reference DE 102 03 609 A1 describes a light wave oven that uses a uniform illumination of the oven chamber by movable linear light sources with a pivotable reflector. This design is very complex from a mechanical standpoint.
The above-described methods also have a disadvantage that they do not accelerate the browning process that requires the long wave portion of the radiation. This disadvantage is described in German Patent Reference DE 102 03 610 A1 and is eliminated through the installation of additional long wave radiation sources with a different color temperature. The additional installation of other radiation sources means that this method is also complex and expensive.
Another known approach is to embody oven walls of glass or glass ceramic. The use of glass ceramic in ovens is known from Canadian Patent Reference CA 2183498, which proposes an oven floor composed of glass ceramic for better cleanability. German Patent Reference DE 33 02 794 A1 describes an oven muffle of glass or glass ceramic, which is heated by printed heating conductors. In this case, it is only possible to produce long wave, slow radiation. German Patent Reference DE 35 27 957 C2 describes an oven muffle of glass ceramic that is detachably assembled and is heated by externally mounted radiant heating elements. The plates are inserted into a supporting or holding frame, and thus the resulting edges and joints, particularly in the lower corner regions of the oven muffle, can only be cleaned with great difficulty. Taking this into account, German Patent Reference DE 35 27 958 C2 discloses an enameled sheet steel muffle, with window openings provided in the side walls, into which the glass or glass ceramic plates are inserted. In this case, the same problem arises because the joints and connections can only be cleaned with difficulty and in addition, a large portion of the muffle chamber is of enameled sheet steel, and as a result the effect of rapid short wave IR radiation is lost.